Add walnuts, sugar and butter. Cook, stirring constantly for approximately 5 minutes so that walnuts are well coated and sugar does not burn.
When walnuts are caramelized, transfer immediately to a baking sheet lined with parchment paper or a silicone mat. Using two forks, work quickly to separate individual walnut pieces so that they will not stick together when cooled.
Once the coating has hardened and the walnuts have cooled, transfer to an airtight container until ready to use. Recipe may be doubled.